Final answer:
Moussa is conducting his research by using a questionnaire, which involves gathering information from subjects through a series of questions.
Step-by-step explanation:
Moussa is conducting his research by using a questionnaire.
A questionnaire is a series of questions that gather information from subjects about their opinions and behaviors. The survey format allows individuals to express their personal ideas while maintaining a level of anonymity.
In this case, Moussa left surveys in random mailboxes in his neighborhood to gather information about his neighbors' thoughts on building a new community playground.